Process of coloring photographic prints.



UNITED STATES PATENT OFFICE.

RUDOLF ISENMANN, 0F NEWARK, NEWV'JERSEY.

PROCESS OF COLORING PHOTOGRAPHIC PRINTS.

Specification of Letters Patent.

Patented Dec. 19, 1905.

Application filed February 18, 1905. Serial No 246,358.

To all whom, it may concern.-

Be it known that I, RUDOLF ISENMANN, a citizen of the United States, residing at Newark, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Processes of Coloring Photographic Prints; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to improvements in color photography, and has for its objects to obtain a process and certain solutions by which color effects can be produced upon daylight or sun paper upon which prints are made from the plate or film.

In carrying out my invention the negative, plate, or film is procured in any ordinary manner common to photography, and prints are made from said negative in the snn'upon any usual sunlight-paper. This paper or print is then exposed to the light or sun until the highlights or light parts are covered or darkened, except, however, the sky effect or clouds, which must not be so darkened. The said sky effect should be clear upon the paper, and to this end, if necessary, the negative or plate must be covered in printing, as by paper, or painting or varnishing to protect it from this darkening. Especially is this necessary if the sky or parts of the sky are rather thin in the negative. The paper or print is then washed with water in any manner common to the art and as will be understood by one skilled in photography. The paper or print is then, in carrying out my invention, immersed in a solution composed of lemon-juice, well known as the crude state of citric acid, and ferricyanid of potassium. Preferably this solution is composed of said elements in the following proportions: From forty to sixty grains of ferricyanid of potassium is dissolved in from five to twenty ounces of Water, and from twenty to thirty drops of this liquid is mixed with one to one and one-half ounces of lemonjuice. The print or paper is, as above stated,

immersed in this solution and left from half a minute to several minutes, after which it is taken out and immediately the sky effect washed in water continuously for about half an hour, the rest of the print outside of said sky effect not being washed. The action of the said solution is to turn the dark portions of the coating of the paper, or those portions which have been printed, to a brownish color. The high lights, such as the sky, are not so affected, however, and are not changed by the first step of my process described above. The print is then immersed in a solution of from one to fifteen grains of ferrous sulfate in from eight to ten ounces of water and left in said solution from three seconds to one minute, after which it is removed and washed in water for from ten minutes to half an hour. This last solution changes the brown or brownish portions of the print more or less completely to green, red, or yellow and varying intermediate shades, while the sky becomes blue.

It will be understood that in carrying out my invention the proportions of ingredients are varied within substantially the limits stated in order to produce different degrees of color and different color effects and that I do not wish to be understood as confining myself either to one definite proportion or to the securing of one definite shade or color, since I may obtain varied results, as above stated, without departing from the spirit and scope of the invention.

Having thus described the invention, what I claim as new is 1. The herein-described process of coloring photographic prints, consisting in darkening a printed paper or print by exposure,washing said paper or print, treating it with a solution of lemon-juice and ferricyanid of potassium,

washing, treating with a solution of ferrous sulfate, and again washing.

2. In a process of coloring photographic prints, the treatment of a print with a solution of lemon-juice and ferricyanid of potassium, and subsequently with a solution of ferrous sulfate, said steps being accompanied by suitable washings.

In testimony that I claim the foregoing I have hereunto set my hand this 4th day of February. 1905.

RUDOLF ISENMANN. Witnesses M. V. DOYLE, RUssnLL M. EVERETT. 

